Expert: Roland Finston - 9/7/2011

Question
QUESTION: Hi, I have a 98 Chrysler sebring jxi that you helped me with before . About a month ago you helped me figure out that my ignition fuse blew, which we replaced and it was fine. Then about 2 weeks ago, my ignition fuse was repeatedly blowing, so you gave me some ideas to try but I had to take it to a mechanic . They said they replaced a few wires, and fuses, and now it starts . They also replaced a spark plug because it was idling very hard, it was misfiring. So now it has gotten progressively worse, the car doesn't want to start without being jumped. We thought it was the battery but got it tested and they said the battery, alternator, cables , wires to battery are all good, just low voltage on battery. The starter is good also. So we thought since they charged the battery it would be ok. However this morning after sitting  all nite it didn't start. Sounds like its about to but never turns completely over. Something must be draining the battery but how do I figure it out? Thanks for your help.
Heh

ANSWER: Hi Jennifer,
There are a number of circuits that are powered when the ignition is nonetheless 'off' so what you need to do to find what is the reason the battery is discharging in an efficient way is to measure the current flowing through the battery using a ammeter inserted between the - post clamp and the - post proper. Usually the flow should be less than 50 milliamps which will not discharge battery unless you fail to use the car for a month or so. If you have access to an ammeter and can check what the present flow is with everything you know of being turned off we can compare that to 50 mA. Then I can tell you which fuses to remove, one at a time, to determine which circuit is overdrawing the battery (the current reading will drop alot). It could be something like the trunk light but we need to have the info about the present amount of what is called the 'ignition off draw' amount of current. There is an 'ignition off draw' fuse (#5 in the box behind the left end-cap of the dash) which would be the prime suspect, but there are other fuses that can have cause 'draw' even when you have the key in the 'off' position. Once we ID the fuse with the largest current 'draw' we can examine what devices are connected to that fuse.
Roland

---------- FOLLOW-UP ----------

QUESTION: Well I don't have an ammeter, is it something I can get fairly inexpensive at an auto parts place? Thanks for your quick response .

Jennifer

Answer
Yes,
Either an Auto Parts or an Electronics Parts/Supply store would have such a device. We are only going to look for DC (not AC) currents of up to 20 milliamps so something light-duty will do, and the device would also measure voltage (up to 20 volts), and resistance (down to 20 ohms) most likely. It should be less than $20 and likely would have a digital readout display.
Roland